Transesterification catalysts fixed on solid support materials

ABSTRACT

A description is given of a process for the transesterification of carboxylic esters, characterized in that the catalyst used is a tin(IV) compound comprising a radical of the formula  
                 
 
     bound to an inorganic support, where L is an at least divalent radical and at least one of the free valences of the Si in formula (I) is bound to the inorganic support, novel tin(IV) compounds and their preparation.

[0001] The present invention relates to immobilized tin-sulfurcatalysts, their preparation and their use in transesterificationreactions of carboxylic esters.

[0002] Transesterification reactions of carboxylic esters can begenerally described by the following reaction scheme:

[0003] in which R is usually a C₁-C₄alkyl radical and R′ and Z are eachan organic radical. The reaction is an equilibrium reaction. In general,the (lower-boiling) alcohol liberated is distilled off during thereaction. A series of different catalysts for this reaction are known(Junzo Otera, Chem. Rev., 93 (1993) 1449-1470), e.g. acids, bases,amines, metal alkoxides and also, inter alia, organotin compounds. Manyof these esterification reactions are carried out at temperatures in therange from 80° C. to above 200° C.

[0004] It is economically advantageous if the reactions can be carriedout in the melt without solvents. A further advantage is gained if theproduct does not have to be purified by distillation or extraction afterthe reaction. For this reason, a catalyst should be able to be used athigh temperatures (reaction in the melt) and the catalyzed reaction mustnot lead to discolored products.

[0005] Organotin compounds are known and very mild catalysts fortransesterifications of carboxylic esters with alcohols. A problemassociated with conventional tin catalysts is achieving an economicalseparation of the tin from the reaction product. A possible solution isthe use of immobilized tin catalysts which can be separated off.

[0006] U.S. Pat. No. 5,436,357 discloses, for example, catalysts boundto polystyrene of the type:

[0007] These compounds are proposed as catalysts fortransesterifications in a temperature range of 50-150° C. They can bedecanted or filtered off and reused a number of times. In most cases,reuse is associated with a drop in activity. No information is givenabout Sn leaching, for example as residual tin content of the product.

[0008] Furthermore, H. Schuhmann and B. Pachaly, J. Organomet. Chem.,233 (1982) 281-289 and H. Schuhmann and B. Pachaly, Angew. Chem., 93(1981) 1092-93 have described the preparation of the following compoundswhich are used stoichiometrically as hydrides for the reduction of alkylhalides.

[0009] These compounds are immobilized on silica gel (or aluminum oxide)and are converted by reduction into the corresponding hydride reagent:

[0010] Essentially the same compounds as in the abovementionedpublications are described in DE 31 19 643.

[0011] The present invention provides a process for thetransesterification of carboxylic esters, characterized in that thecatalyst used is a tin(IV) compound comprising a radical of the formula

[0012] bound to an inorganic support, where L is an at least divalentradical and at least one of the free valences of the Si in formula (I)is bound to the inorganic support.

[0013] These immobilized tin-sulfur catalysts can be used in a widetemperature range and, after the reaction, can be separated from thereaction product simply and completely by solid/liquid separationoperations, for example filtration, centrifugation and decantation. Thecatalysts which have been filtered off continue to be catalyticallyactive and can be reused a number of times.

[0014] The process of the invention is particularly suitable forpreparing compounds of the general formula

[0015] in which

[0016] R₁₀₁ and R₁₀₂ are identical or different and are H, alkyl havingfrom 1 to 18 C atoms, phenyl, C₁-C₄alkyl-substituted phenyl, phenylalkylhaving from 7 to 9 C atoms, C₅-C₁₂cycloalkyl, C₁-C₄alkyl-substitutedC₅-C₁₂cycloalkyl or a radical

[0017] R₁₀₃ is H or CH₃;

[0018] R₁₀₅ is H, Cl, —SO₃H or C₁-C₄alkyl;

[0019] m is 0, 1, 2 or 3; and

[0020] n is 1, 2, 3 or 4; where,

[0021] when n=1,

[0022] A is —OR₁₀₄; and

[0023] R₁₀₄ is alkyl having from 2 to 45 C atoms, C₂-C₄₅alkylinterrupted by one or more oxygen, cycloalkyl having from 5 to 12 Catoms, alkenyl having from 2 to 18 C atoms, —CH₂CHOHCH₂OC(O)R₁₀₉ or—CH₂CH₂—OR₁₀₆; and

[0024] R₁₀₉ is H, alkyl having from 1 to 8 C atoms, alkenyl having from3 to 5 C atoms or benzyl; where

[0025] R₁₁₂ is

[0026] H, alkyl having from 1 to 24 C atoms, phenyl, cycloalkyl havingfrom 5 to 12 C atoms or

[0027] and

[0028] R₁₁₀ is H or —CH₃;

[0029] R₁₁₁ is H or alkyl having from 1 to 24 C atoms; and

[0030] R₁₁₂ is H or —CH₃, with the proviso that R₁₁₀ and R₁₁₂ are notsimultaneously —CH₃;

[0031] or, when n=2,

[0032] A is —O—C_(x)H_(2x)—O—, —O—(CH₂CH₂O)_(a)CH₂CH₂O— or—O—CH₂CH═CHCH₂—O—; in which

[0033] a is from 1 to 30; and

[0034] x is from 2 to 20;

[0035] or, when n=3,

[0036] A is

[0037] R₁₀₇ is alkyl having from 1 to 24 C atoms or phenyl,

[0038] or, when n=4,

[0039] A is

[0040] The process is particularly preferred for preparing compounds ofthe formula (X) in which n is one;

[0041] R₁₀₁ is tert-butyl or

[0042] R₁₀₂ is tert-butyl;

[0043] R₁₀₃ and R₁₀₅ are H;

[0044] m is 2; A is OR₁₀₄;

[0045] R₁₀₄ is (CH₂)₁₇CH₃, C₈H₁₇ (isomer mixture), C₂-C₄₅alkylinterrupted by one or more oxygen, —CH₂CHOHCH₂OC(O)R₁₀₉; and

[0046] R₁₀₉ is alkenyl having from 3 to 5 C atoms;

[0047] or n is 2;

[0048] R₁₀₁ is tert-butyl or

[0049] R₁₀₂ is CH₃;

[0050] R₁₀₃ is H;

[0051] m is 2;

[0052] A is —O—(CH₂CH₂O)_(a)CH₂CH₂O—; and

[0053] a is from 1 to 30;

[0054] or n is 3;

[0055] R₁₀₁ and R₁₀₂ are tert-butyl;

[0056] R₁₀₃ is H;

[0057] m is 2; and

[0058] A is —O—CH₂—CH(O—)—CH₂—O—;

[0059] or n is 4;

[0060] R₁₀₁ and R₁₀₂ are tert-butyl;

[0061] R₁₀₃ is H;

[0062] m is 2; and

[0063] A is C(CH₂—O—)₄.

[0064] The process of the invention is likewise suitable for preparingcompounds of the general formula

[0065] in which

[0066] R₂₀₀ and R₂₀₁ are, independently of one another, C₁-C₄alkyl;

[0067] R₂₀₂ is H, C₁-C₁₈alkyl, O or C₁-C₁₈alkoxy;

[0068] A₂₀₀ is, when p=1, C₁-C₁₂alkyl, C₁-C₁₂alkyl substituted by—C(O)OH or C₂-C₅alkenyl; or, when p=2, C₁-C₁₂alkylene; and

[0069] p is 1 or 2.

[0070] The process of the invention is likewise suitable for preparingcompounds which are obtainable by reaction of a compound of the formula

[0071] in which

[0072] R₂₁₀ and R₂₁₁ are, independently of one another, C₁-C₄alkyl; and

[0073] x is from 1 to 12;

[0074] with a compound of the formula

R₂₁₂OC(O)—A₂₁₀—(O)COR₂₁₃  (XXXI)

[0075] in which

[0076] R₂₁₂ and R₂₁₃ are, independently of one another, C₁-C₄alkyl; and

[0077] A₂₁₀ is C₁-C₁₂alkylene.

[0078] The compounds obtainable by reaction of the compounds (XXX) with(XXXI) are, in general, oligomeric or polymeric compounds or mixtures ofsuch compounds. The stoichiometric ratios and reaction parameters makeit possible to influence the formation of the compounds or mixtures ofcompounds.

[0079] Examples of the substituents in the formulae (X), (XX), (XXX) and(XXXI) are given below.

[0080] Alkyl having up to 45 C atoms can be a linear or branched alkylgroup and can be, for example: methyl, ethyl, propyl, isopropyl,n-butyl, isobutyl, t-butyl, pentyl, isopentyl, hexyl, heptyl, 3-heptyl,octyl, 2-ethylhexyl, nonyl, decyl, undecyl, dodecyl, tridecyl,tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, 2-ethylbutyl,1-methylpentyl, 1,3-dimethylbutyl, 1,1,3,3-tetramethylbutyl,1-methylhexyl, isoheptyl, 1-methylheptyl, 1,1,3-trimethylhexyl,1-methylundecyl, eicosyl, henicosyl, docosyl, triacontyl and others.Preference is given to alkyl having 1-12 C atoms and particularpreference is given to alkyl having 1-8 C atoms. When mention is made ofi-C₈H₁₇, this is to be understood as including a mixture of isomers.

[0081] A very particularly preferred example of R₁₀₁ and R₁₀₂ is thet-butyl group. Preference is also given to R₁₀₁═—CH₃ and R₁₀₂═t-butyl orR₁₀₁═isopropyl and R₁₀₂═t-butyl. As R₁₀₃, preference is given to —H.Preferred R₁₁₁, R₁₀₇ and R₁₀₆ are alkyl groups having from 1 to 18 Catoms.

[0082] Examples of cycloalkyl substituents having from 5 to 12 C atomsare cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclodecyl andcyclododecyl. Preference is given to cyclohexyl.

[0083] Examples of C₁-C₄alkyl-substituted cycloalkyl having from 5 to 12C atoms are 2- or 4-methylcyclohexyl, dimethylcyclohexyl,trimethylcyclohexyl and t-butylcyclohexyl.

[0084] Examples of C₁-C₄alkyl-substituted phenyl substituents aremethylphenyl, dimethylphenyl, trimethylphenyl, ethylphenyl,diethylphenyl, isopropylphenyl and 6-butylphenyl.

[0085] Examples of phenylalkyl having from 7 to 9 C atoms are benzyl,phenethyl, α-methylbenzyl and α,α-dimethylbenzyl. Preference is given tobenzyl.

[0086] Alkenyl having up to 18 C atoms is, for example, vinyl, propenyl,allyl, butenyl, methallyl, hexenyl, decenyl or heptadecenyl.

[0087] When m=2, the group described is, for example, —CH₂—CH₂—; whenm=3, the group described is, for example, —CH₂—CH₂—CH₂— or—CH₂—CH(CH₃)—.

[0088] The tin(IV) compounds which can be used as catalysts in theprocess of the invention are, in general, mixtures of compounds ofvarious compositions. Preference is given to compounds or mixtures ofcompounds obtainable by reaction of a compound of the formula:

[0089] in which

[0090] t is 1, 2 or 3;

[0091] u is 0, 1 or 2;

[0092] v is 1, 2, 3, 4, 5, 6, 7, 8 or 9; and

[0093] w is 1, 2 or 3,

[0094] with the proviso that t+u+w=4;

[0095] L is an at least divalent C₁-C₁₈alkylene, C₂-C₁₈alkenylene,phenylene, C₁-C₁₈alkylene/phenylene radical or C₂-C₁₈alkylene orC₁-C₁₈alkylene/phenylene radical interrupted by one or more O, C(O), S,C(S), N(Y), C(O)—N(Y), N(Y)—C(O)—N(Y) and/or N(Y)—C(O)—O;

[0096] Support is an inorganic support material;

[0097] R₁ are, independently of one another, C₁-C₄alkoxy, phenoxy,C₁-C₄alkyl, phenyl or halogen; and

[0098] Y are, independently of one another, C₁-C₁₈alkyl, phenyl orC₁-C₁₈alkyl/phenyl;

[0099] with a compound of the formula

Sn[R₂]₄  (IIb),

[0100] in which

[0101] R₂ are, independently of one another, C₁-C₁₈alkyl, substitutedC₁-C₁₈alkyl, C₂-C₁₈alkenyl, C₁-C₁₈haloalkyl, C₆-C₁₆haloaryl,C₃-C₁₆haloheteroaryl, C₁-C₄alkylphenyl, C₁-C₄alkoxyphenyl,halo-C₁-C₄alkylphenyl, halo-C₁-C₄alkoxyphenyl, C₁-C₁₂hydroxyalkyl,C₃-C₈cycloalkyl, C₆-C₁₆aryl, substituted C₆-C₁₆aryl, C₇-C₁₆aralkyl,C₃-C₆heterocycloalkyl, C₃-C₁₆heteroaryl, C₄-C₁₆heteroaralkyl, —Cl, —Br,—I, OH, —OC₁—C₁₈alkyl, —OC₆—C₁₆aryl, —OOC—C₁-C₁₈alkyl, —OOC-phenyl, SH,—N(Si(CH₃)₃)₂, SC₁-C₁₈alkyl, —SC₆-C₁₆aryl, —SC(O)—C₁-C₁₈alkyl,—SC(O)-phenyl, —SC(S)—C₁-C₁₈alkyl, —SC(S)-phenyl, H or an oxygen bridgeto a further Sn atom;

[0102] or two radicals R₂ are together ═S or ═O,

[0103] with the proviso that at least one R₂ radical which can reactwith an SH group to form an S—Sn bond is present.

[0104] L is preferably C₁-C₁₈alkylene, C₂-C₁₈alkenylene, phenylene orC₁-C₁₈alkylene/phenylene, particularly preferably C₁-C₁₈alkylene, veryparticularly preferably C₂-C₆alkylene.

[0105] R₁ is preferably C₁-C₄alkoxy, particularly preferably methoxy orethoxy.

[0106] R₂ is preferably halogen, OH or ═O, particularly preferablychlorine.

[0107] Examples of an at least divalent C₁-C₁₈alkylene radical arelinear or branched C₁-C₁₈alkylene radicals of the type mentioned furtherbelow in which at least one further H atom is replaced by a direct bond,for example —CH₂—, —CH₂CH₂—, —C(CH₃)₂—, —CH₂C(CH₃)CH₂—, ═CH— or—CH₂CHCH₂—.

[0108] At least divalent C₂-C₁₈alkenylene radicals are analogous to theat least divalent alkylene radicals described; they have one or more C—Cdouble bonds.

[0109] Examples of at least divalent phenylene radicals are o-phenyleneor p-phenylene.

[0110] At least divalent C₁-C₁₈alkylene/phenylene radicals are derivedfrom the at least divalent alkylene radicals described by the alkylenechain being interrupted by phenylene, where phenylene can also form thebeginning and/or the end of the chain.

[0111] At least divalent C₂-C₁₈alkylene or C₂-C₁₈alkylene/phenyleneradicals interrupted by one or more O, C(O), S, C(S), N(Y), C(O)—N(Y),N(Y)—C(O)—N(Y) and/or N(Y)—C(O)—O are derived from the analogous atleast divalent radicals described; in the case of a plurality ofinterrupting radicals, these are generally not directly adjacent.Examples of radicals of this type in which the interrupting radicals canalso form the beginning and/or the end of the chain are:—CH₂CH₂—O—CH₂—CH₂—, —CH₂—C₆H₄—CH₂—O—CH₂—, —CH₂—CH₂—C(O)—CH₂,—CH₂—CH₂—C(O), —CH₂—CH—CH₂—CH₂—N(C₂H₅)—CH₂—CH₂—O— or—CH₂—CH₂—CH—CH₂—O—CH₂—CH₂—O—.

[0112] Trivalent alkylene radicals L are, for example,

[0113] with the proviso that the sum of the C atoms is not more than 18.

[0114] In the above definitions, halogen is to be understood as beingfluorine, chlorine, bromine or iodine. In the case of a plurality ofhalogen substituents, these can be of the same type or mixed (forexample Cl and F).

[0115] Alkyl is methyl, ethyl, isopropyl, n-propyl, n-butyl, iso-butyl,sec-butyl, tert-butyl or the various isomeric pentyl, hexyl, heptyl,octyl, nonyl, decyl, undecyl or dodecyl radicals. Haloalkyl is, forexample, fluoromethyl, difluoromethyl, trifluoromethyl, chloromethyl,dichloromethyl, trichloromethyl, 2,2,2-trifluoroethyl, 2-fluoroethyl,2-chloroethyl or 2,2,2-trichloroethyl; preferably trichloromethyl,difluorochloromethyl, trifluoromethyl or dichlorofluoromethyl.

[0116] Alkoxy is, for example, methoxy, ethoxy, propyloxy, i-propyloxy,n-butyloxy, i-butyloxy, s-butyloxy or t-butyloxy; preferably methoxy orethoxy.

[0117] Haloalkoxy is, for example, fluoromethoxy, difluoromethoxy,trifluoromethoxy, 2,2,2-trifluoroethoxy, 1,1,2,2-tetrafluoroethoxy,2-fluoroethoxy, 2-chloroethoxy or 2,2,2-trichloroethoxy; preferablydifluoromethoxy, 2-chloroethoxy or trifluoromethoxy.

[0118] Cycloalkyl is, for example, cyclopropyl, dimethylcyclopropyl,cyclobutyl, cyclopentyl, methylcyclopentyl, cyclohexyl or cycloheptyl,preferably cyclopropyl, cyclopentyl or cyclohexyl.

[0119] Alkoxyalkyl is, for example: methoxymethyl, ethoxymethyl,propyloxymethyl, methoxyethyl, ethoxyethyl, propyloxyethyl,methoxypropyl, ethoxypropyl or propyloxypropyl.

[0120] Phenyl, including phenyl as part of a substituent such asphenoxy, phenylthio, phenoxycarbonyl, phenylaminocarbonyl, benzyl orbenzoyl, can in general be present in unsubstituted form or besubstituted by further substituents. The substituents can then be in theortho, meta and/or para positions. Preferred substituent positions arethe ortho and para positions relative to the ring linkage point.Preferred substituents are halogen atoms.

[0121] Aralkyl is, for example, benzyl, phenylethyl, 3-phenylpropyl,α-methylbenzyl, phenylbutyl or α,α-dimethylbenzyl.

[0122] Aryl and analogously haloaryl are, for example, phenyl, tetralin,indene, naphthalene, azulene or anthracene.

[0123] Heteroaryl and analogously haloheteroaryl are, for example,pyrrole, furan, thiophene, oxazole, thiazole, pyridine, pyrazine,pyrimidine, pyridazine, indole, purine, quinoline or isoquinoline.

[0124] Heterocycloalkyl is, for example, oxirane, oxetane, azetidine,azirine, 1,2-oxathiolane, pyrazoline, pyrrolidine, piperidine,piperazine, morpholine, dioxolane, tetrahydropyran, tetrahydrofuran ortetrahydrothiophene.

[0125] The inorganic support materials are preferably glass, silicates,semimetal oxides and metal oxides which are particularly preferably inthe form of powder having a mean particle diameter of from 10 nm to 5mm. The particles can be compact or porous. Porous particles preferablyhave a high internal surface area, for example 1-1200 m²/g. Furtherpreferred support materials are inorganic support materials containingOH groups. Examples of oxides and silicates are SiO₂, TiO₂, ZrO₂, MgO,NiO, WO₃, Al₂O₃, La₂O₃, silica gels, clays and zeolites. Particularlypreferred support materials are silica gels, aerosils, aluminum oxide,titanium oxide and mixtures thereof. An example of glass as supportmaterial is “controlled pore glass”, which is commercially available.

[0126] A further aspect of the present invention is a tin(IV) compoundcomprising a radical of the formula

[0127] bound to an inorganic support, where L is an at least divalentradical and at least one of the free valences of the Si in formula (I)is bound to the inorganic support, with the exception of tin(IV)compounds which have two or three hydrocarbon radicals on the Sn andonly one tin-sulfur bond and the Si is bound via the three free valencesto an OH-containing inorganic support.

[0128] Preferred immobilized tin(IV) compounds comprise a radical of theformula (Ia)

[0129] in which L is a divalent radical and at least one of the freevalences of each Si in formula (Ia) is bound to the inorganic support.

[0130] Likewise preferred immobilized tin(IV) compounds are those whichcomprise a radical of the formula (Ib)

[0131] in which L is a trivalent radical and at least one of the freevalences of Si in formula (Ib) is bound to the inorganic support. Themeanings of L, including the preferences, are indicated above.

[0132] Preference is also given to immobilized tin(IV) compounds ormixtures of compounds obtainable by reaction of a compound of theformula:

[0133] in which

[0134] t is 1, 2 or 3;

[0135] u is 0, 1 or 2;

[0136] v is 1, 2, 3, 4, 5, 6, 7, 8 or 9; and

[0137] w is 1, 2 or 3,

[0138] with the proviso that t+u+w=4;

[0139] L is an at least divalent C₁-C₁₈alkylene, C₂-C₁₈alkenylene,phenylene, C₁-C₁₈alkylene/phenylene radical or C₂-C₁₈alkylene orC₁-C₁₈alkylene/phenylene radical interrupted by one or more O, C(O), S,C(S), N(Y), C(O)—N(Y), N(Y)—C(O)—N(Y) and/or N(Y)—C(O)—O;

[0140] Support is an inorganic support material:

[0141] R₁ are, independently of one another, C₁-C₄alkoxy, phenoxy,C₁-C₄alkyl, phenyl or halogen; and

[0142] Y are, independently of one another, C₁-C₁₈alkyl, phenyl orC₁-C₁₈alkyl/phenyl;

[0143] with a compound of the formula

Sn[R₂]₄  (IIb),

[0144] in which

[0145] R₂ are, independently of one another, C₁-C₁₈alkyl, substitutedC₁-C₁₈alkyl, C₂-C₁₈alkenyl, C₁-C₁₈haloalkyl, C₆-C₁₆haloaryl,C₃-C₁₆haloheteroaryl, C₁-C₄alkylphenyl, C₁-C₄alkoxyphenyl,halo-C₁-C₄alkylphenyl, halo-C₁-C₄alkoxyphenyl, C₁-C₁₂hydroxyalkyl,C₃-C₈cycloalkyl, C₆-C₁₆aryl, substituted C₆-C₁₆aryl, C₇-C₁₆aralkyl,C₃-C₆heterocycloalkyl, C₃-C₁₆heteroaryl, C₄-C₁₆heteroaralkyl, —Cl, —Br,—I, OH, —OC₁-C₁₈alkyl, —OC₆-C₁₆aryl, —OOC—C₁-C₁₈alkyl, —OOC-phenyl, SH,—N(Si(CH₃)₃)₂, SC₁-C₁₈alkyl, —SC₆-C₁₆aryl, —SC(O)—C₁-C₁₈alkyl,—SC(O)-phenyl, —SC(S)—C₁-C₁₈alkyl, —SC(S)-phenyl, H or an oxygen bridgeto a further Sn atom;

[0146] or two radicals R₂ together are ═S or ═O,

[0147] with the proviso that at least one R₂ radical which can reactwith an SH group to form an S—Sn bond is present.

[0148] Preferably, t is 2 or 3, u is 0 or 1, v is 1 or 2 and w is 1 or2.

[0149] Examples of compounds comprising a radical of the formula (I) orof compounds obtainable by reaction of compounds of the formulae (IIa)and (IIb) are:

[0150] in which the substituents are as defined above and Support

Si is the bond to the inorganic support material and any furtherradicals R₁ bound to Si, with the proviso that the total number of bondson the Si is 4.

[0151] Support

Si can be illustrated by

[0152] In general, no uniform bond is obtained.

[0153] A further aspect of the present invention is the preparation ofthe tin(IV) compounds bound to (immobilized on) an inorganic supportwhich are according to the invention or can be used according to theinvention. This can be carried out in various ways which are known inprinciple. In the following, two basic methods of preparation aredescribed by way of example.

[0154] Method 1: A thiol is first immobilized and the immobilized thiolis subsequently reacted with a tin(IV) compound.

[0155] Immobilization of the thiol:

[0156] in which

[0157] L, v and w are as defined above, including the preferences;

[0158] R₁′ is C₁-C₄alkyl or phenyl;

[0159] R₁″ are, independently of one another, C₁-C₄alkoxy, phenoxy orhalogen; and

[0160] i is 0, 1 or 2, with the proviso that w+i is less than 4.

[0161] The immobilization of alkoxy silanes and halosilanes on aninorganic support has been comprehensively described in the literature(for example by: K. K. Unger, Porous Silica, in Journal ofChromatography Library, Vol 16, Elsevier Scientific Publishing Company(1979)). The loading density (mmol of thiol/g of support) of the Sithiol can be controlled within a wide range by means of the amount of Sithiol used relative to the amount of support used and by means of theimmobilization conditions. The Si thiol compound is usually dissolved ina solvent (e.g. xylene, toluene, benzene, THF, methylene chloride, ethylacetate or ether). Preference is given to nonpolar and high-boilingsolvents. This solution is then added to the support (or vice versa) andthe mixture is typically stirred gently for 3-50 hours, preferably forabout 10-20 hours, at temperatures of from 50° C. to the refluxtemperature. The water formed or the alcohol formed is distilled off.The product is then filtered off and washed with a suitable solvent(e.g. alcohol) to remove any excess thiol. The product can subsequentlybe dried at elevated temperature, preferably under reduced pressure, orit can be directly, without drying, slurried in a solvent suitable forthe reaction with Sn(IV) compounds. To prevent possible oxidation of thethiol to corresponding disulfides, the procedure can be carried outunder inert gas (e.g. nitrogen, argon) if necessary.

[0162] It is also possible to obtain thiol-containing solids(polysiloxanes) by condensation of “Si thiol” compounds either alone ortogether with alkoxysilanes. Examples are given in DE 30 29 599(crosslinking of metal-phosphine-Si(OR)₃ complexes with H₂O to givepolysiloxanes and also crosslinking of phosphine-Si(OR)₃ to givepolysiloxanes and subsequent formation of metal complexes). A review maybe found, for example, in C. J. Brinker, G. W. Scherrer, Buch: Sol GelScience, Academic Press (1990).

[0163] The immobilized thiols are subsequently reacted with Sn(IV).(General literature on the preparation of Sn compounds having Sn—Sbonds: Gmelin, 8th edition, tin). These can be either pure Sn(R₂)₄compounds or mixtures of various Sn(R₂)₄ compounds. The 4 radicals R₂can be identical or different. At least one R₂ has to be a radical whichcan react with a thiol group to form an S—Sn bond. Compounds having aradical R₂ of this type are preferably halides, alkoxides, carbonates orSn compounds having OH or Sn═O groups. It is also known that Sn(alkyl)₄compounds can react with thiols to form an Sn—S bond. The Sn(IV)compound is generally dissolved in a suitable solvent (e.g. linear andcyclic alkanes, aromatics such as benzene or toluene, halogenatedhydrocarbons, nitromethane, DMSO, alcohols, acetone, carboxylic acidssuch as acetic acid, esters, DMF, nitrites and also water) and thesolution is added to the Si thiol fixed on the support, or vice versa.The addition can be carried out at temperatures of from −78° C. to 100°C. In the case of Sn-halogen compounds, the reaction with the Si thiolcan result in liberation of hydrohalic acid. This can be neutralized bymeans of bases (for example alkalis, carbonates, ammonia, amines). Afterthe Sn(IV) compound(s) and the Si thiol have been combined, the reactionmixture is stirred slowly at temperatures of from 20° C. to the boilingpoint of the solvent. The reaction time is typically from 1 hour to anumber of days. The product is then filtered off, washed with solventssuch as alcohols, water, and, if necessary, after-treated with aslightly basic aqueous solution or a solution which modifies the ligandor ligands. The ratio of S to Sn can be controlled via the amount ofSn(IV) which is added relative to the amount of thiol immobilized on thesupport. The ratio of S/Sn can vary in the range from 1:1 to 10:1.

[0164] The ratio of S/Sn can also be changed afterwards bycoproportionation with an Sn(IV) compound.

[0165] The immobilized catalysts can be used without drying or they canbe dried at elevated temperature (preferably under reduced pressure)before use and, if necessary, also be thermally treated before use, forexample at a temperature in the range 100° C.-300° C.

[0166] Instead of the immobilization of thiols, it is also possible toimmobilize disulfides, for example of the following types, in the mannerdescribed above for the thiols:

[0167] in which the substituents are as defined above, including theirpreferences, and i is 1-3.

[0168] Such disulfides are known or can be prepared in a simple way byknown methods (W. Buder, Z. Naturforsch., 34b (1979) 790-793). Some ofthem are commercially available and are described, for example, in thecompany document “Chemieforschung im Degussa ForschungszentrumWolfgang”, Volume 1, pages 94-99, 1988.

[0169] The immobilized disulfides can subsequently be either

[0170] a) reacted directly with Sn compounds:

[0171] or

[0172] b) first reduced to thiols or thiolates (e.g. using Na₂S, K₂S,glucose, sodium dithionite, phosphine) and subsequently reacted withSn(IV) compounds as described for the thiols.

[0173] The invention therefore also provides a process for preparingcompounds of the formula (I) according to claim 1 immobilized oninorganic supports by reacting a compound of the formula:

[0174] in which

[0175] t is 1, 2 or 3;

[0176] u is 0, 1 or 2;

[0177] v is 1, 2, 3, 4, 5, 6, 7, 8 or 9; and

[0178] w is 1, 2 or 3,

[0179] with the proviso that t+u+w=4;

[0180] L is an at least divalent C₁-C₁₈alkylene, C₂-C₁₈alkenylene,phenylene, C₁-C₁₈alkylene/phenylene radical or a C₂-C₁₈alkylene orC₁-C₁₈alkylene/phenylene radical interrupted by one or more O, C(O), S,C(S), N(Y), C(O)—N(Y), N(Y)—C(O)—N(Y) and/or N(Y)—C(O)—O;

[0181] Support is an inorganic support material;

[0182] R₁ are, independently of one another, C₁-C₄alkoxy, phenoxy,C₁-C₄alkyl, phenyl or halogen; and

[0183] Y are, independently of one another, C₁-C₁₈alkyl, phenyl orC₁-C₁₈alkylphenyl;

[0184] with a compound of the formula

Sn[R₂]₄  (IIb),

[0185] in which

[0186] R₂ are, independently of one another, C₁-C₁₈alkyl, substitutedC₁-C₁₈alkyl, C₂-C₁₈alkenyl, C₁-C₁₈haloalkyl, C₆-C₁₆haloaryl,C₃-C₁₆haloheteroaryl, C₁-C₄alkylphenyl, C₁-C₄alkoxyphenyl,halo-C₁-C₄alkylphenyl, halo-C₁-C₄alkoxyphenyl, C₁-C₁₂hydroxyalkyl,C₃-C₈cycloalkyl, C₆-C₁₆aryl, substituted C₆-C₁₆aryl, C₇-C₁₆aralkyl,C₃-C₆heterocycloalkyl, C₃-C₁₆heteroaryl, C₄-C₁₆heteroaralkyl, —Cl, —Br,—I, OH, —OC₁-C₁₈alkyl, —OC₆-C₁₆aryl, —OOC—C₁-C₁₈alkyl, —OOC-phenyl, SH,—N(Si(CH₃)₃)₂, SC₁-C₁₈alkyl, —SC₆-C₁₆aryl, —SC(O)—C₁-C₁₈alkyl,—SC(O)-phenyl, —SC(S)—C₁-C₁₈alkyl, —SC(S)-phenyl, H or an oxygen bridgeto a further Sn atom;

[0187] or two radicals R₂ are together ═S or ═O,

[0188] with the proviso that at least one R₂ radical which can reactwith an SH group to form an S—Sn bond is present.

[0189] Method 2: Firstly preparation of an, if desired isolated,immobilized Sn—S compound and then immobilization of this compound.(General literature on the preparation of Sn compounds having Sn—Sbonds: Gmelin, 8th edition, tin). Pure immobilized Sn—S compounds ormixtures thereof are obtained by reacting n^(o) compounds of the typeSi—SM having n^(o).v.w SM groups either partially or completely withcompounds Sn(R₂)₄ so as to form at least one Sn—S bond.

[0190] The substituents and the indices i, v and w are as defined above,including their preferences, M is H or an alkali metal, preferably Na, Kor Li, and n^(o) is 1-4, preferably 1-3.

[0191] Examples of the compounds formed are shown below.

[0192] If at least one R₂ is halogen, the immobilizable Sn—S compoundsare prepared by reaction of the thiol or a thiolate with Sn(R₂)₄. In thereaction with the thiol, the hydrohalic acid formed can be neutralizedby means of a base (e.g. alkalis, carbonates, ammonia, amines).

[0193] If at least one R₂ is O-alkyl, O-aryl, OH or N(alkyl)₂ or two R₂are together a double bond to oxygen, the immobilizable Sn—S compoundsare prepared by reaction of the thiol with Sn(R₂)₄. If necessary, theHO-alkyl, HO-aryl, H₂O or amine formed during the reaction can bedistilled off.

[0194] It is also known that Sn(alkyl)₄ compounds can react with thiolsto form an Sn—S bond (Gmelin).

[0195] Where a plurality of R₂ can react with the thiol/thiolate, thepreferred stoichiometry on the Sn can be set by selection of thethiol/Sn ratio.

[0196] The immobilizable Sn—S compounds can be immobilized on a supportor polycondensed in a manner analogous to that for the thiol compounds(see Method 1).

[0197] The invention therefore likewise provides a further process forpreparing a tin(IV) compound bound to an inorganic support,characterized in that a compound of the formula

[0198] is reacted with a compound of the formula Sn(R₂)₄ to form animmobilizable Sn—S compound and this compound is immobilized on aninorganic support,

[0199] where

[0200] (R₁)′ is C₁-C₄alkyl or phenyl;

[0201] (R₁)″ are, independently of one another, C₁-C₄alkoxy, phenoxy orhalogen; and

[0202] i is 0, 1 or 2, with the proviso that w+i is less than or equalto 4;

[0203] v is 1, 2, 3 or 4; and

[0204] w is 1, 2 or 3;

[0205] L is an at least divalent C₁-C₁₈alkylene, C₂-C₁₈alkenylene,phenylene, C₁-C₁₈alkylene/phenylene radical or a C₂-C₁₈alkylene orC₁-C₁₈alkylene/phenylene radical interrupted by one or more O, C(O), S,C(S), N(Y), C(O)—N(Y), N(Y)—C(O)—N(Y) and/or N(Y)—C(O)—O;

[0206] Support is an inorganic support material;

[0207] R₂ are, independently of one another, C₁-C₄alkoxy, phenoxy,C₁-C₄alkyl, phenyl or halogen; and

[0208] Y are, independently of one another, C₁-C₁₈alkyl, phenyl orC₁-C₁₈alkyl/phenyl;

[0209] n^(o) is 1, 2, 3 or 4; and

[0210] M is H or an alkali metal.

[0211] After the immobilization, the immobilized catalysts can be usedwithout drying or can be dried at elevated temperature (preferably underreduced pressure) before use and can, if necessary, also be thermallytreated before use (at temperatures in the range 100° C.-300° C.).

[0212] The catalyst can be present in dispersed form in the reactantsand is filtered off after the reaction is complete. The catalyst whichhas become exhausted by use can be regenerated and reused or else can bediscarded. It is also possible to arrange the catalyst in a fixed bedand to carry out the reaction in, for example, a flow reactor(continuous process).

[0213] The transesterification is advantageously carried out by reactingthe starting materials either in the form of a solution in a solvent or,if they are not liquid, in the form of a melt produced by increasing thetemperature.

[0214] Solvents employed are the compounds and mixtures which arecustomary per se, for example aromatic hydrocarbons such as benzene andalkyl-substituted or halogenated benzenes, in particular toluene, xyleneor dichlorobenzene, high-boiling aliphatic hydrocarbons such ashigh-boiling paraffins, aprotic solvents such as dimethylformamide ordimethylaniline.

[0215] The catalyst is added to the reaction mixture in amounts of, forexample, from 0.001 to 10 mol %, advantageously from 0.01 to 1 mol %, ofactive material, based on the compounds comprising a radical of theformula (I).

[0216] The ratio of carboxylic ester and alcohol in the reaction mixtureis not critical and can be, for example, from 0.8 to 1.3 mol of thecarboxylic ester per equivalent of the alcohol.

[0217] The reaction temperature can be, for example, from 110 to 250°C., preferably from 130 to 210° C.

[0218] The transesterification of the carboxylic esters generally takesfrom 1 to 10 hours, advantageously from 1 to 5 hours and preferably from1 to 3 hours, to achieve optimum yields.

[0219] The catalyst can, for example, be present as a suspension in thereaction mixture in the form of powder through to broken pieces. Use ofthe catalyst in a fixed bed is a further possible way of carrying outthe process.

[0220] After the reaction has ended, the catalyst can, if it was presentin suspension, be separated off, for example filtered off, and the endproduct can be isolated by methods known per se, for examplecrystallization from a solvent such as methanol, isopropanol,methanol/water mixture, etc.

[0221] If necessary, the reaction mixture and/or the end product can beneutralized using an acid, e.g. formic acid, acetic acid, sulfuric acid,hydrochloric acid, etc.

[0222] The carboxylic esters and alcohols used in the process of theinvention are known or can be obtained by methods known per se.

[0223] The invention further provides for the use of a tin(IV) compoundcomprising a radical of the formula

[0224] bound to an inorganic support, where L is an at least divalentradical and at least one of the free valences of the Si in formula (I)is bound to the inorganic support, as catalyst in thetransesterification of carboxylic esters.

[0225] The carboxylic esters prepared according to the invention are,for example, valuable antioxidants against oxidative, thermal or actinicdegradation of sensitive organic materials. Such materials are, forexample, synthetic polymers of functional liquids such as lubricants,hydraulic fluids or metalworking fluids, etc.

EXAMPLES A) Immobilization of Thiols and Disulfides

[0226] All reactions are carried out under inert gas.

[0227] General Procedure for Immobilizing3-mercaptopropyltrimethoxysilane

[0228] 100 g of support are stirred in 700 ml of toluene in an inert gasatmosphere and dried by distilling off 200-300 ml of toluene. Aftercooling to about 40° C., 40 ml (0.215 mol) of3-mercaptopropyltrimethoxysilane are added, the mixture is againdistilled briefly and subsequently stirred for 20 hours at 100°-110° C.,ensuring that the methanol formed can distill off. After cooling, thesupport is filtered off, washed with 2×200 ml of each of ethyl acetate,methanol and hexane and finally dried under reduced pressure (1 mbar) at70° C. for 15 hours.

Example A1

[0229] 20 g of dried silica gel (Merck 100) (2 hours at 110° C. in avacuum oven) are suspended in 80 ml of dried toluene in a flask fittedwith a stirrer and treated with 10 g (51 mmol) of3-mercaptopropyltrimethoxysilane (Fluka, purum). The mixture is stirredfor 12 hours at 100° C. and the methanol formed is distilled off. Thesolid is then filtered off and washed 4 times with 100 ml of methanol.Finally, the functionalized silica gel is dried under reduced pressureat 70-100° C. This gives 22.4 g of product having an S content of 2.85%.This corresponds to a loading density of 0.89 mmol of thio compound perg of material.

[0230] Examples A2-A9 are carried out according to the above-describedgeneral procedure, giving the results shown in Table 1 for thecorresponding variations. TABLE 1 Preparation, deviation from theprocedure Analysis of Loading Ex. No. Support described S content mmolS/g A2 Silica gel Batch using only 20 g of support, drying of 2.85% 0.89Merck 100 the silica gel not by azeotropic distillation in toluene butunder reduced pressure (5 mbar) at 120° C. for 2 hours. Immobilizationin 80 ml of toluene and 0.05 mol of 3-mercaptopropyltrimethoxy- silane.Washing only with methanol. A3 Silica gel 0.260 mol of3-mercaptopropyltrimethoxy- 2.33% 0.73 Merck 100 silane added. Washingonly with methanol. A4 Silica gel, As in procedure described 1.65% 0.52Grace 332 A5 Silica gel, Drying of the silica gel not by azeotropic0.75%  0.234 Grace 332 distillation in toluene but in high vacuum (0.1mbar) at 140° C. for 4 hours. A6 and Silica gel, After addition of3-mercaptopropyltri- 2.98% 0.93 A7 Grace 332 methoxysilane, 0.5 ml ofmethanesulfonic acid added. A8 and Silica gel 0.269 mol of3-mercaptopropyltrimethoxy- 2.73% 0.85 A9 Merck 100 silane added.Washing only with methanol.

Example A10

[0231] Immobilization of bis(3-triethoxysilylpropyl) disulfide

[0232] The bis(3-triethoxysilylpropyl) disulfide is prepared by a methodanalogous to that described by W. Buder, Z. Naturforsch., 34b (1979)790-793.

[0233] 50 g of silica gel Merck 100 are stirred in 250 ml of toluene inan inert gas atmosphere and dried by distilling off about 50 ml oftoluene. After cooling to about 40° C., 23.7 g (0.05 mol) ofbis(3-triethoxysilylpropyl) disulfide are added, the mixture is againdistilled briefly and subsequently stirred at 100°-110° C. for 20 hours,ensuring that the ethanol formed can distill off. After cooling, thesupport is filtered off, washed with 2×100 ml of each of ethyl acetate,methanol and hexane and finally dried under reduced pressure (1 mbar) at70° C. for 15 hours. This gives white material having an S content of1.83%. This corresponds to a loading density of 0.29 mmol of disulfideper g.

B) Preparation of the Tin(IV) Catalysts

[0234] All reactions are carried out under inert gas.

Example B1

[0235] 8 g of the thio compound fixed to silica gel from Example A1 aresuspended in 60 ml of hexane, cooled to 0° C. and slowly treated with5.12 g of an 18.1% solution of SnCl₄ in hexane. After 15 minutes, 0.8 gof triethylamine is added and the mixture is stirred for 2 hours at roomtemperature. Finally, the product is filtered off, washed first withhexane, then with a sodium carbonate solution and with water and thendried overnight under reduced pressure at 80° C. This gives 8.1 g ofproduct having an S content of 2.7% and an Sn content of 2.46%. Thiscorresponds to an Sn loading density of 0.201 mmol/g and a ratio of Snto S of about 1:4.

Examples B2-B16

[0236] The results of the reaction of immobilized sulfur compounds withSnCl₄ and the variations of the experimental parameters are summarizedin Table 2. (MW in kg means weight of product in kg per mol of Sn) TABLE2 Summary of the SnCl₄ —S catalysts Analy- Analy- Cat. Support- sis sisMW No. SH Support Remarks 5% Sn % S/Sn kg B2 A2 Merck 2.7 2.46 4.1 4.8100 B3 A3 Merck 2.24 3.25 2.55 3.64 100 B4 A6 Grace 2.75 3.34 3.1 3.57332 B5 A6 Grace 2.8 3.28 3.2 3.63 332 B6 A6 Grace 2.83 3.1 3.4 3.84 332B7 A6 Grace 2.71 2.57 3.9 4.63 332 B8 A6 Grace 2.84 2.01 5.3 5.96 332 B9A6 Grace 2.74 3.88 2.63 3.07 332 B10 A6 Grace 2.78 3.44 3 3.46 332 B11A5 Grace 0.72 1.06 2.53 11.2 332 B12 A8 Merck 2.42 3.8 2.37 3.13 100 B13Integrated Merck 1.89 2.22 3.2 5.34 100 B14 A7 Grace 2.8 5.13 2.03 2.33332 B15 A7 Grace 2.8 4.86 2.15 2.45 332 B16 A6 Grace Copropor- 2.85 4.262.5 2.8 332 tionation #reduced pressure (5 mbar) at 80° C. for 15 hours.#the white product is dried under reduced pressure (5 mbar) at 80° C.for 15 hours. #2 × hexane), the white product is dried under reducedpressure (5 mbar) at 80° C. for 15 hours. #the white product is driedunder reduced pressure (5 mbar) at 80° C. for 15 hours. #After cooling,the support is filtered off and washed with 2 × 200 ml of methanol. (Asmall sample is dried and analyzed → S content: 1.93%). Half of themethanol-moist material (30 mmol of S) is slurried in 150 ml of tolueneand slowly treated while stirring at room temperature with 3.9 g (15mmol) of SnCl₄ and subsequently with a freshly prepared sodium methoxidesolution in methanol (30 mmol of sodium in 35 ml of methanol). Themixture is stirred for 4 hours at room temperature, #then filtered,washed (2 × 100 ml each of methanol, NaHCO₃ 2M, water, methanol) and theproduct is dried under reduced pressure (5 mbar) at 80° C. for 15 hours.#The tin content of the product is 30% higher than that of Example B5.

[0237] The results of the reaction of immobilized alkyl thiols withvarious Sn(IV) compounds and the various experimental conditions aresummarized in Table 3. TABLE 3 Summary of various Sn(IV) compounds.Examples B17-29 Cat. Support- Sn Analysis Analysis MW No. SH compound S% Sn % S/Sn kg B17 A4 Bu2SnO 1.51 4.11 1.36 2.9  B18 A4 Ph2SnO 1.48 3.351.65 3.57 B19 A4 BuSnCl3 1.53 3.14 1.81 3.79 B20 A4 BuSnCl3 1.51 2.682.01 4.44 B21 A4 BuSnCl3 1.63 2.01 3.02 5.92 B22 A4 PhSnCl3 1.46 2.622.1  4.55 B23 A4 Bu3SnCl 1.49 3.94 1.41 3.02 B24 A4 Ph3SnOH 1.41 4.461.18 2.57 B25 A4 BuSnO)OH 1.6  2.77 2.15 4.3  B26 A4 ‘Sn(OEt)4’ 1.6 3.44 1.72 3.0  B27 A6 Bu2SnOAc 2.72 4.26 2.37 2.8  B28 A6 BuSn(OH)2Cl2.42 3.8  2.37 3.14 B29 A9 BuSn(OH)2Cl 2.54 4.36 2.17 2.75 ar) at 50° C.for 15 hours. . for 15 hours. exane) the white prodct is dried underreduced pressure (5 mbar) at 50° C. for 15 hours. e 95 mbar to 50° C.for 15 hours. bar at 60° C. for 15 hours. , 2 × hexane) and the whiteproduct is dried under reduced pressure (5 mbar) at 70° C. for 15 hours.educed pressure (5 mbar) at 70° C. for 15 hours.

[0238] Immobilization of Sn(IV)—S Compounds Having TrialkoxysilaneRadicals

[0239] Preparation of the Sn(IV)—S Compounds Having TrialkoxysilaneRadicals

[0240] B30 Preparation of (Bu)₂Sn[S(CH₂)₃Si(OCH₃)₃]₂

[0241] 2 HS(CH₂)₃Si(OCH₃)₃+(Bu)₂SnCl₂+2(C₂H₅)₃N→(Bu)₂Sn[S(CH₂)₃Si(OCH₃)₃]₂+2 (C₂H₅)₃N*HCl

[0242] 98.2 g (0.50 mol) of 3-mercaptopropyltrimethoxysilane and 52.6 g(0.52 mol) of triethylamine together with 200 ml of n-hexane are placedin a reaction vessel. Subsequently, a solution of 76.0 g (0.25 mol) ofdibutyltin dichloride in 300 ml of n-hexane is metered in over a periodof about 20 minutes and the reservoir is rinsed with 200 ml of n-hexane.The internal temperature rises from 20 to 35° C. during this step. Awhite solid starts to precipitate right at the beginning of the meteredaddition. After stirring for 24 hours at about 20° C., the precipitateis filtered off, the filtrate and the residues are washed with 200 ml ofn-hexane. The still slightly turbid filtrates are combined andevaporated in a double-wall reactor to a temperature of about 61° C. and1 hPa, which results in disappearance of the turbidity. At 20° C., about143 g of a slighty yellowish, liquid product are drained off (91.8% oftheory). Microanalysis: S 10.44%, Sn 19.2%.

[0243] B31 Preparation of (Bu)₂SnCl[S(CH₂)₃Si(OCH₃)₃]

[0244] (Bu)₂Sn[S(CH₂)₃Si(OCH₃)₃]₂+(Bu)₂SnCl₂→2(Bu)₂SnCl[S(CH₂)₃Si(OCH₃)₃]

[0245] In a test tube, 24.3 g (0.080 mol) of tributyltin dichloride aredissolved in 49.9 g (0.080 mol) of the compound from Example B30 whilewarming gently (about 50° C.) and allowed to stand for 2 days at roomtemperature. Microanalysis: S 6.29%, Sn 26.5%

[0246] B32 Preparation of (Ph)₂Sn[S(CH₂)₃Si(OCH₃)₃]₂

[0247] 2 HS(CH₂)₃Si(OCH₃)₃+(Ph)₂SnCl₂+2(C₂H₅)₃N→(Ph)₂Sn[S(CH₂)₃Si(OCH₃)₃]₂+2 (C₂H₅)₃N*HCl

[0248] Method of preparation analogous to Example B30 except that 86 g(0.25 mol) of diphenyltin dichloride are used in place of dibutyltindichloride. The liquid product is obtained in a yield of 87.5%.Microanalysis: S 10.12%, Sn 17.1%

[0249] B33 Preparation of Sn[S(CH₂)₃Si(OCH₃)₃]₄

[0250] 4 HS(CH₂)₃Si(OCH₃)₃+SnCl₄+4 (C₂H₅)₃N→Sn[S(CH₂)₃Si(OCH₃)₃]₄+4(C₂H₅)₃N*HCl

[0251] 98.2 g (0.50 mol) of 3-mercaptopropyltrimethoxysilane and 50.6 g(0.50 mol) of triethylamine together with 200 ml of n-hexane are placedin a reaction vessel. Subseuquently, a solution of 32.6 g (0.125 mol) oftin tetrachloride in 250 ml of n-hexane is metered in over a period ofabout 45 minutes. The further procedure is the same as in Example B30.The liquid product is obtained in a yield of 85.1%. Microanalysis: S12.2%, Sn 14.5%

[0252] B34 Preparation of SnCl_(4−n)[S(CH₂)₃Si(OCH₃)₃]_(n)

[0253] Sn[S(CH₂)₃Si(OCH₃)₃]₄+SnCl₄→2 SnCl_(4−n)[S(CH₂)₃Si(OCH₃)₃]_(n)

[0254]40.0 g (0.044 mol) of the compound from Example B33 are placed inan argon-blanketed test tube and 11.6 g (0.044 mol) of tin tetrachlorideare stirred in. The reaction is exothermic and a white solid isprecipitated. Microanalysis: liquid part of the mixture: S 12.3%, Sn14.5%; solid part: S 10.24%, Sn 21.8%.

[0255] B35: Immobilization of the Compound from Example B30 1412/21

[0256] (Bu)₂Sn[S(CH₂)₃Si(OCH₃)₃]₂

[0257] A suspension of 40 g of silica gel Merck 100 in 300 ml of tolueneis first dried by azeotropic distillation of 100 ml of toluene. Aftercooling to room temperature, 31.2 g of the tin compound 1412/21 areadded, the mixture is briefly distilled and stirred for 18 hours at 100°C., ensuring that the alcohol formed can distill off. After cooling, theproduct is filtered off, washed (100 ml each: 3×methanol, 3×ethylacetate, 3×hexane) and dried under reduced pressure (5 mbar) at 70° C.for 15 hours.

[0258] B36: Immobilization of the Compound from Example B32(Ph)₂Sn[S(CH₂)₃Si(OCH₃)₃]₂

[0259] Prepared the same way as in Example B35, except that the reactionis carried out using 33.7 g of the Sn compound from Example B32.

[0260] B37: Immobilization of the compound from Example B31(Bu)₂SnCl[S(CH₂)₃Si(OCH₃)₃]

[0261] Prepared the same way as in Example B35, except that the reactionis carried out using 23.1 g of the Sn compound from Example B31 and thatwashing is carried out as follows: 100 ml each; 3×methanol, 1×NaHCO₃ 1M,3×water, 3×methanol, 2×ethyl acetate, 2×hexane.

[0262] B38: Immobilization of the Compound from Example B34SnCl_(4−n)[S(CH₂)₃Si(OCH₃)₃]_(n)

[0263] Prepared the same way as in Example B35, except that the reactionis carried out using 29 g of the Sn compound B34 and that washing iscarried out as follows: 100 ml each: 3×methanol, 1×NaHCO₃ 1M, 3×water,3×methanol, 2×ethyl acetate, 2×hexane.

[0264] The results are summarized in Table 4. TABLE 4 Immobilization ofSn(IV)-S compounds having trialkoxysilane radicals Sn Cat. compoundAnalysis Analysis MW No. Support No. Sn compound S % Sn % S/Sn kg B35Merck B30 ((MeO)₃Si-C₃H₆- 1.94 4.2  1.72 2.84 100 S)₂SnBu₂ B36 Merck B32((MeO)₃Si-C₃H₆- 2.36 3.86 2.28 3.01 100 S)₂SnPh₂ B37 Merck B31((MeO)₃Si-C₃H₆- 2.16 4.4  1.82 2.71 100 S)Sn(Bu)₂Cl B38 Merck B34((MeO)₃Si-C₃H₆- 4.58 3.48 4.9  3.35 100 B S)_(n)SnCl_(4-n)

[0265] Preparation of Sn—S Compounds by Sol-Gel Processes

[0266] Sol-gel processes are described, for example, in the followingpublications:

[0267] C. J. Brinker, G. W. Scherrer, book: Sol Gel Science, AcademicPress (1990).

[0268] L. L. Hench and J. K. West, Chem. Rev., 90 (1990) 33-72.

[0269] U. Schubert et al., J. Non Cryst. Solids, 105 (1988) 165-170.

[0270] P. Panster, CLB Chemie in Labor und Biotechnik, 43 (1992) 16-21.

[0271] These processes can be used in an analogous way for theimmobilization of the catalysts of the invention. Examples B39 and 40illustrate this.

[0272] B39

[0273] 5.42 g (6 mmol) of ((CH₃O)₃Si—C₃H₆—S)₄Sn (compound from ExampleB33), 7.3 g (48 mmol) of tetramethoxysilane, 1.56 g (6 mmol) of tintetrachloride and 100 ml of acetone are combined while stirring in aflask. 34 ml of a 2.8N phosphoric acid solution are added dropwise tothe above solution over a period of 30 minutes. The resulting solutionis allowed to stand for 4 days in an open vessel, resulting inevaporation of the acetone and formation of a yellowish-white mass. Thisis stirred for 14 hours in 200 ml of water, filtered off, washed (30 mleach: 3×methanol, 1×NaHCO₃ 2M, 3×water, 3×methanol, 2×ethyl acetate,2×hexane) and dried under reduced pressure (5 mbar) at 70° C. for 15hours.

[0274] B40

[0275] 2.83 g of triethylamine are added to a solution of 7.92 g (52mmol) of tetramethoxysilane, 0.94 g (4 mmol) of n-octyltrimethoxysilane,2.75 g (14 mmol) of 3-mercaptopropyltrimethoxysilane, 100 ml of acetoneand 1.82 g (7 mmol) of tin tetrachloride, resulting in formation of awhite precipitate. 35 ml of a 2.8N phosphoric acid solution are addeddropwise to this mixture over a period of 30 minutes. The resultingclear solution is allowed to stand for 6 days in an open vessel,resulting in evaporation of the acetone and formation of ayellowish-white mass. This is partially dried overnight at 70° C. underreduced pressure (5 mbar), washed (50 ml each: 3×methanol, 1×NaHCO₃ 2M,3×water, 3×methanol, 2×ethyl acetate, 2×hexane) and dried under reducedpressure (5 mbar) at 70° C. for 15 hours.

[0276] The results are summarized in Table 5. TABLE 5 Sn catalystsprepared by sol-gel processes: Analysis Analysis MW Cat. No. CompositionS % Sn % S/Sn kg B39 ((MeO)₃Si-C₃H₆-S)₄Sn, SnCl₄, (MeO)₄Si 6.62 10.42.64 1.28 B40 (MeO)₃Si-C₃H₆-SH, SnCl₄, (MeO)₄Si, n-Octyl- 5.1  7.45 2.551.6  Si(OMe)₃

[0277] Immobilization of Sn—S Compounds on Disulfides Bound to Supports

[0278] B41

[0279] 8 g of a material (Deloxan® DSP from Degussa) prepared asdescribed in the literature (U. Deschler et al., Angew. Chemie., 98(1986) 237-53; P. Panster, CLB Chemie in Labor und Biotechnik, 43 (1992)16-21) by copolycondensation of bis(3-trialkoxysilylpropyl) disulfideand having a sulfur content of 19.7% are dried in 50 ml of toluene byazeotropic distillation of 20 ml of toluene. After cooling, a solutionof 1.68 g (3.69 mmol) of Sn(N(SiCH₃)₂)₂ in 15 ml of toluene is addeddropwise at room temperature. The mixture is then stirred for 15 hoursat 70° C. and for another 2 hours at 120° C. After cooling to roomtemperature, it is filtered, washed (30 ml each: 3×methanol, 1×NaHCO₃2M, 3×water, 3×methanol, 2×ethyl acetate, 2×hexane) and dried underreduced pressure (5 mbar) at 70° C. for 15 hours.

[0280] B42

[0281] 10 g of the disulfide bound to silica gel from Example A10 in 70ml of toluene are dried by azeotropic distillation of 40 ml of toluene.After cooling, a solution of 1.26 g (2.85 mmol) of Sn(N(SiCH₃)₂)₂ in 10ml of toluene is added dropwise at room temperature. The furtherprocedure is analogous to Example B41.

[0282] B43

[0283] Reduction of the disulfide to thiol: 90 ml of methanol, 10 ml of1,4-dioxane, 10 ml of water, 5 g of triphenylphosphine and 1 ml ofmethanesulfonic acid are added to 16 g of the disulfide described inPU732.1 and the mixture is stirred at 70° C. for 17 hours. Subsequently,the product is filtered off and washed with 700 ml of methanol/toluene.Reaction with SnCl₄: 0.74 g of sodium acetate is added while stirring tohalf of the moist product in 30 ml of methanol and, subsequently, 1.04 gof tin tetrachloride are slowly added. After 2 hours, the mixture isfiltered and washed (40 ml each: 1×MeOH, 1×H₂O, 2×NaHCO₃ 2M, 3×water,3×MeOH) and dried under reduced pressure (5 mbar) at 70° C. for 15hours. TABLE 6 Sn catalysts based on immobilized dialkyl disulfides: Im-mob. Anal- di- y- Analy- Cat. sul- sis sis MW No. Support fide Sncompound S % Sn % S/Sn kg B41 Deloxan DSP Sn(N(SiCH₃)₂)₂ 18.39 4.28 162.8 B42 Merck A10 Sn(N(SiCH₃)₂)₂ 1.64 2.86 2.14 4.17 100 B43 Deloxan DSPSnCl₄ 17.93 5.34 12.5 2.23 reduced

C) Use Examples Example C1

[0284]

[0285] 17.5 g of compound (101) (60 mmol) and 13.5 g of stearyl alcohol(50 mmol) are melted at 120° C. in a rotary evaporator. 2 g of thecatalyst from Example B1 are then added and, under reduced pressure (100mbar), the temperature is increased to 190° C. over a period of 30minutes. The vacuum is then improved to 8 mbar over a period of 1 hour20 minutes. After a further 30 minutes, the melt is then filtered andthe catalyst is reused. In 4 reuses of the catalyst, a conversion of85-90% according to GC is obtained in each case and the product in eachcase contains less than 1 ppm of Sn.

Example C2

[0286] 142.6 g (0.489 mol) of compound (101) and 120.35 g (0.445 mol) ofstearyl alcohol are placed in a sulfation flask and heated to 180° C.under inert gas. 15.39 g of catalyst from Example B3 are added to thismelt. The apparatus is evacuated to 3 mbar, the contents are stirred at180° C. for 4 hours and the methanol formed is continuously distilledoff. Subsequently, the mixture is cooled to 150° C. and filtered. Reuse:The unwashed catalyst can be reused as described above.

[0287] Results Results: Conversion based on stearyl alcohol used ppm oftin in crude Catalyst use (GC) product Fresh cat. 76.8%  2 1st reuse95.8% <1 2nd reuse 98.2%  1 3rd reuse 99.6% <1 4th reuse 99.9% <1 5threuse 99.5% <1

[0288] In all cases the selectivity is greater than 99%. Thetransmission at 425 nm is over 99% in all reuses.

[0289] The catalyst is still active even after the 5th reuse.

Example C3

[0290] The procedure is the same as described in Example C2. Batch size:30.2 g (0.111 mol) of compound (101), 25.6 g (0.101 mol) of stearylalcohol, 2.79 g of catalyst from Example B12.

[0291] Results Results: Conversion based on stearyl alcohol used ppm oftin in crude Catalyst use (GC) product Fresh cat. 61.4% 2 1st reuse89.9% 1 2nd reuse 98.6% <1  3rd reuse 95.6% 1 4th reuse 97.5% 2 5threuse 97.5% <1 

[0292] In all cases, the selectivity is greater than 99%. Thetransmission at 425 nm is above 99% in all reuses.

[0293] The catalyst is still active even after the 5th reuse.

Example C4

[0294] The procedure is the same as for Mü19. Batch size: 30.2 g (0.111mol) of compound (101), 25.6 g (0.101 mol) of stearyl alcohol, 1.28 g ofcatalyst from Example B17.

[0295] Results Results: Conversion based on stearyl alcohol used ppm oftin in crude Catalyst use (GC) product Fresh catalyst 75.5% 8 1st reuse91.1% 5

[0296] In all cases, the selectivity is greater than 99%. Thetransmission at 425 nm is above 99% in the reuse.

[0297] The catalyst is still active even after the 1st reuse.

Example C5

[0298] The procedure is the same as that described in Example C2. Batchsize: 33 g (0.12 mol) of compound (1019), 25.5 g (0.101 mol) of stearylalcohol, 2.18 g of catalyst from Example B20.

[0299] Results Results: Conversion based on stearyl alcohol used ppm oftin in crude Catalyst use (GC) product Fresh catalyst 87.5%  8 1st reuse78.5% 10

[0300] In all cases, the selectivity is greater than 99%. Thetransmission at 425 [lacuna] is above 96%.

Example C6

[0301] The procedure is the same as that described in Example C2. Batchsize: 30.2 g (0.111 mol) of compound (101), 25.6 g (0.101 mol) ofstearyl alcohol, 1.26 g of catalyst from Example B28.

[0302] Results Results: Conversion based on stearyl alcohol used ppm oftin in crude Catalyst use (GC) product Fresh catalyst 98.7%  4 1st reuse99.4% <2

[0303] In all cases, the selectivity is greater than 99%. Thetransmission at 425 nm is above 99% in the reuse.

[0304] The catalyst is still active even after the 1st reuse.

Example C7

[0305] The procedure is the same as that described in Example C2. Batchsize: 30.2 g (0.111 mol) of compound (101), 25.6 g (0.101 mol) ofstearyl alcohol, 1.1 g of catalyst from Example B25.

[0306] Results Results: Conversion based on stearyl alcohol used ppm oftin in crude Catalyst use (GC) product Fresh catalyst 62.8% 2 1st reuse82.1% 1

[0307] In all cases, the selectivity is greater than 99%. Thetransmission at 425 nm is above 99% in the reuse.

[0308] The catalyst is still active even after the 1st reuse.

Example C8

[0309] The procedure is the same as that described in Example C2. Batchsize: 129.7 g (0.445 mol) of compound (101), 120.4 g (0.445 mol) ofstearyl alcohol, 2.974 g of catalyst from Example B35.

[0310] Results Results: Conversion based on stearyl alcohol used ppm oftin in crude Catalyst use (GC) product Fresh catalyst 92.9% 28 1st reuse  96% 17

[0311] In all cases, the selectivity is greater than 99%. Thetransmission at 425 nm is above 99% in the reuse.

[0312] The catalyst is still active even after the 1st reuse.

Example C9

[0313] The procedure is the same as that described in Example C2. Batchsize: 30.2 g (0.111 mol) of compound (101), 25.6 g (0.101 mol) ofstearyl alcohol, 1.24 g of catalyst from Example B41.

[0314] Results Results: Conversion based on stearyl alcohol used ppm oftin in crude Catalyst use (GC) product Fresh catalyst 99.77% <1 1streuse 98.5% 1

[0315] In all cases, the selectivity is greater than 99%. Thetransmission at 425 nm is above 99% in the reuse.

[0316] The catalyst is still active even after the 1st reuse.

Example C10

[0317] The procedure is the same as that described in Example C2. Batchsize: 30.2 g (0.111 mol) of compound (101), 25.6 g (0.101 mol) ofstearyl alcohol, 3.72 g of catalyst from Example B42.

[0318] Results Results: Conversion based on stearyl alcohol used ppm oftin in crude Catalyst use (GC) product Fresh catalyst 85.2% 5 1st reuse86.7% 5

[0319] In all cases, the selectivity is greater than 99%. Thetransmission at 425 nm is above 98%.

[0320] The catalyst is still active even after the 1st reuse.

Example C11

[0321]

[0322] The catalyst described in Example B3 is used for the abovetransesterification. 4.0 g of catalyst, 100 g of compound (103) and 73.7g of isooctanol isomer mixture are placed in a stirred glass reactorprovided with a reflux condenser heated to 80° C. and a vacuum pump. Thereactor is subsequently evacuated to 400 mbar and the reaction mixtureis heated to reflux temperature while stirring. The methanol formed inthe reaction is distilled off through the reflux condenser heated to 80°C. and is condensed in a downstream cold trap. After about 4 hours, aboiling temperature of the reaction mixture of 180-185° C. is reached.After further reaction for 3 hours, a conversion of 99.8% at aselectivity of almost 100% in respect of the initially charged methylester is achieved. After cooling the reaction mixture to 120° C., thecatalyst is filtered off and reused in the next 2 reaction batches.Here, the filtered-off, unwashed catalyst is again mixed with 100 g ofmethyl ester, compound (103) and 73.7 g of isooctanol and the reactionis carried out using the above procedure. A conversion of 99.6% isachieved after only 5 hours. The selectivity is likewise almost 100%.The residual tin content of the product is 30 ppm both in the first testand also in the 2 recycling tests.

Example C12

[0323] Preparation ofTetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyloxymethyl]methaneCompound (105)

[0324] 250.0 g (0.856 mol) of methyl3,5-bis(1,1-dimethyl)-4-hydroxyphenylpropionate [sic] (101), 23.3 g(0.171 mol) and 5.12 g of catalyst from Example B29 are heated to 180°C. and held at this temperature for 6.5 hours. During this time, thepressure is gradually reduced to 3 mbar. 15.2 g (0.47 mol, 70% oftheory) of the reaction product (105) are obtained. The catalyst isrecovered by filtration. A clear, colorless product is obtained.

Example C13

[0325] Transesterification of a Glyceride Mixture with Methyl3,5-bis(1,1-dimethyl)-4-hydroxyphenyl-propionate [sic] (101)

[0326] 65.0 g of coconut oil (about 0.096 mol), 50.9 g of glycerol 86.6%(0.48 mol), 292.4 g of methyl3,5-bis(1,1-dimethylethyl)-4-hydroxyphenylpropionate (101) (1.00 mol)and 8.0 g of catalyst from Example B29 are slowly heated while stirringto 200° C. in a 1 liter flask provided with a dephlegmator at 60° C., acondenser at 15-20° C. and a cold trap at −80° C., with a pressure of200 mbar being set. The temperature is held at 200° C. for two hours andthe pressure is reduced from 200 mbar to 20 mbar over a period of onehour. 6.6 g of water and 30.0 g of methanol are taken off. The catalystis recovered by filtration. 343.4 g of product are obtained as a clear,yellowish resin.

1. Process for the transesterification of carboxylic esters,characterized in that the catalyst used is a tin(IV) compound comprisinga radical of the formula

bound to an inorganic support, where L is an at least divalent radicaland at least one of the free valences of the Si in formula (I) is boundto the inorganic support.
 2. Process according to claim 1 for preparingcompounds of the formula (X)

in which R₁₀₁ and R₁₀₂ are identical or different and are H, alkylhaving from 1 to 18 C atoms, phenyl, C₁-C₄alkyl-substituted phenyl,phenylalkyl having from 7 to 9 C atoms, C₅-C₁₂cycloalkyl,C₁-C₄alkyl-substituted C₅-C₁₂cycloalkyl or a radical

R₁₀₃ is H or CH₃; R₁₀₅ is H, Cl, —SO₃H or C₁-C₄alkyl; m is 0, 1, 2 or 3;and n is 1, 2, 3 or 4; where, when n=1, A is —OR₁₀₄; and R₁₀₄ is alkylhaving from 2 to 45 C atoms, C₂-C₄₅alkyl interrupted by one or moreoxygen, cycloalkyl having from 5 to 12 C atoms, alkenyl having from 2 to18 C atoms, —CH₂CHOHCH₂OC(O)R₁₀₉ or —CH₂CH₂—OR₁₀₆; and R₁₀₉ is H, alkylhaving from 1 to 8 C atoms, alkenyl having from 3 to 5 C atoms orbenzyl; where R₁₀₆ is

H, alkyl having from 1 to 24 C atoms, phenyl, cycloalkyl having from 5to 12 C atoms or

and R₁₁₀ is H or —CH₃; R₁₁₁ is H or alkyl having from 1 to 24 C atoms;and R₁₁₂ is H or —CH₃, with the proviso that R₁₁₀ and R₁₁₂ are notsimultaneously —CH₃; or, when n=2, A is —O—C_(x)H_(2x)—O—,—O—(CH₂CH₂O)_(a)CH₂CH₂O— or —O—CH₂CH═CHCH₂—O—; in which a is from 1 to30; and x is from 2 to 20; or, when n=3, A is

in which R₁₀₇ is alkyl having from 1 to 24 C atoms or phenyl, or, whenn=4, A is


3. Process according to claim 2 for preparing compounds of the formula(X) in which n is one; R₁₀₁ is tert-butyl or

R₁₀₂ is tert-butyl; R₁₀₃ and R₁₀₅ are H; m is 2; A is OR₁₀₄; R₁₀₄ is(CH₂)₁₇CH₃, C₈H₁₇ (isomer mixture), C₂-C₄₅alkyl interrupted by one ormore oxygen, —CH₂CHOHCH₂OC(O)R₁₀₉; and R₁₀₉ is alkenyl having from 3 to5 C atoms; or n is 2; R₁₀₁ is tert-butyl or

R₁₀₂ is CH₃; R₁₀₃ is H; m is 2; A is —O—(CH₂CH₂O)_(a)CH₂CH₂O—; and a isfrom 1 to 30; or n is 3; R₁₀₁ and R₁₀₂ are tert-butyl; R₁₀₃ is H; m is2; and A is —O—CH₂—CH(O—)—CH₂—O—; or n is 4; R₁₀₁ and R₁₀₂ aretert-butyl; R₁₀₃ is H; m is 2; and A is C(CH₂—O—)₄.
 4. Process accordingto claim 1 for preparing compounds of the formula (XX)

in which R₂₀₀ and R₂₀₁ are, independently of one another, C₁-C₄alkyl;R₂₀₂ is H, C₁-C₁₈alkyl, O or C₁-C₁₈alkoxy; A₂₀₀ is, when p=1,C₁-C₁₂alkyl, C₁-C₁₂alkyl substituted by —C(O)OH or C₂-C₅alkenyl; or,when p=2, C₁-C₁₂alkylene; and p is 1 or
 2. 5. Process according to claim1 for preparing carboxylic esters by reaction of a compound of theformula (XXX)

in which R₂₁₀ and R₂₁₁ are, independently of one another, C₁-C₄alkyl;and x is from 1 to 12; with a compound of the formulaR₂₁₂OC(O)—A₂₁₀—(O)COR₂₁₃  (XXXI) in which R₂₁₂ and R₂₁₃ are,independently of one another, C₁-C₄alkyl; and A₂₁₀ is C₁-C₁₂alkylene. 6.Process according to claim 1, wherein the catalyst is a compound or amixture of compounds obtainable by reaction of a compound of the formula(IIa)

in which t is 1, 2 or 3; u is 0, 1 or 2; v is 1, 2, 3, 4, 5, 6, 7, 8 or9; and w is 1, 2 or 3, with the proviso that t+u+w=4; L is an at leastdivalent C₁-C₁₈alkylene, C₂-C₁₈alkenylene, phenylene,C₁-C₁₈alkylene/phenylene radical or C₂-C₁₈alkylene orC₁-C₁₈alkylene/phenylene radical interrupted by one or more O, C(O), S,C(S), N(Y), C(O)—N(Y), N(Y)—C(O)—N(Y) and/or N(Y)—C(O)—O; Support is aninorganic support material; R₁ are, independently of one another,C₁-C₄alkoxy, phenoxy, C₁-C₄alkyl, phenyl or halogen; and Y are,independently of one another, C₁-C₁₈alkyl, phenyl or C₁-C₁₈alkyl/phenyl;with a compound of the formula Sn[R₂]₄  (IIb), in which R₂ are,independently of one another, C₁-C₁₈alkyl, substituted C₁-C₁₈alkyl,C₂-C₁₈alkenyl, C₁-C₁₈haloalkyl, C₆-C₁₆haloaryl, C₃-C₁₆haloheteroaryl,C₁-C₄alkylphenyl, C₁-C₄alkoxyphenyl, halo-C₁-C₄alkylphenyl,halo-C₁-C₄alkoxyphenyl, C₁-C₁₂hydroxyalkyl, C₃-C₈cycloalkyl, C₆-C₁₆aryl,substituted C₆-C₁₆aryl, C₇-C₁₆aralkyl, C₃-C₆heterocycloalkyl,C₃-C₁₆heteroaryl, C₄-C₁₆heteroaralkyl, —Cl, —Br, —I, OH, —OC₁-C₁₈alkyl,—OC₆-C₁₆aryl, —OOC—C₁-C₁₈alkyl, —OOC-phenyl, SH, —N(Si(CH₃)₃)₂,SC₁-C₁₈alkyl, —SC₆-C₁₆aryl, —SC(O)—C₁-C₁₈alkyl, —SC(O)-phenyl,—SC(S)—C₁-C₁₈alkyl, —SC(S)-phenyl, H or an oxygen bridge to a further Snatom; or two radicals R₂ are together ═S or ═O, with the proviso that atleast one R₂ radical which can react with an SH group to form an S—Snbond is present.
 7. Tin(IV) compound comprising a radical of the formula

bound to an inorganic support, where L is an at least divalent radicaland at least one of the free valences of the Si in formula (I) is boundto the inorganic support, with the exception of tin(IV) compounds whichhave two or three hydrocarbon radicals on the Sn and only one tin-sulfurbond and the Si is bound via the three free valences to an OH-containinginorganic support.
 8. Immobilized tin(IV) compounds or mixtures ofcompounds according to claim 7, obtainable by reaction of a compound ofthe formula (IIa)

in which t is 1, 2 or 3; u is 0, 1 or 2; v is 1, 2, 3, 4, 5, 6, 7, 8 or9; and w is 1, 2 or 3, with the proviso that t+u+w=4; L is an at leastdivalent C₁-C₁₈alkylene, C₂-C₁₈alkenylene, phenylene,C₁—C₁₈alkylene/phenylene radical or C₂-C₁₈alkylene orC₁-C₁₈alkylene/phenylene radical interrupted by one or more O, C(O), S,C(S), N(Y), C(O)—N(Y), N(Y)—C(O)—N(Y) and/or N(Y)—C(O)—O; Support is aninorganic support material: R₁ are, independently of one another,C₁-C₄alkoxy, phenoxy, C₁-C₄alkyl, phenyl or halogen; and Y are,independently of one another, C₁-C₁₈alkyl, phenyl or C₁-C₁₈alkyl/phenyl;with a compound of the formula Sn[R₂]₄  (IIb), in which R₂ are,independently of one another, C₁-C₁₈alkyl, substituted C₁-C₁₈alkyl,C₂-C₁₈alkenyl, C₁-C₁₈haloalkyl, C₆-C₁₆haloaryl, C₃-C₁₆haloheteroaryl,C₁-C₄alkylphenyl, C₁-C₄alkoxyphenyl, halo-C₁-C₄alkylphenyl,halo-C₁-C₄alkoxyphenyl, C₁-C₁₂hydroxyalkyl, C₃-C₈cycloalkyl, C₆-C₁₆aryl,substituted C₆-C₁₆aryl, C₇-C₁₆aralkyl, C₃-C₆heterocycloalkyl,C₃-C₁₆heteroaryl, C₄-C₁₆heteroaralkyl, —Cl, —Br, —I, OH, —OC₁-C₁₈alkyl,—OC₆-C₁₆aryl, —OOC—C₁-C₁₈alkyl, —OOC-phenyl, SH, —N(Si(CH₃)₃)₂,SC₁-C₁₈alkyl, —SC₆-C₁₆aryl, —SC(O)—C₁-C₁₈alkyl, —SC(O)-phenyl,—SC(S)—C₁-C₁₈alkyl, —SC(S)-phenyl, H or an oxygen bridge to a further Snatom; or two radicals R₂ together are ═S or ═O, with the proviso that atleast one R₂ one [sic] radical which can react with an SH group to forman S—Sn bond is present.
 9. Compound according to claim 7, wherein theinorganic support material is a material selected from the groupconsisting of SiO₂, TiO₂, ZrO₂, MgO, NiO, WO₃, Al₂O₃, La₂O₃, silicagels, clays and zeolite.
 10. Process for preparing compounds of theformula (I) according to claim 1 immobilized on inorganic supports,characterized in that a compound of the formula:

in which t is 1, 2 or 3; u is 0, 1 or 2; v is 1, 2, 3, 4, 5, 6, 7, 8 or9; and w is 1, 2 or 3, with the proviso that t+u+w=4; L is an at leastdivalent C₁-C₁₈alkylene, C₂-C₁₈alkenylene, phenylene,C₁-C₁₈alkylene/phenylene radical or a C₂-C₁₈alkylene orC₁-C₁₈alkylene/phenylene radical interrupted by one or more O, C(O), S,C(S), N(Y), C(O)—N(Y), N(Y)—C(O)—N(Y) and/or N(Y)—C(O)—O; Support is aninorganic support material; R₁ are, independently of one another,C₁-C₄alkoxy, phenoxy, C₁-C₄alkyl, phenyl or halogen; and Y are,independently of one another, C₁-C₁₈alkyl, phenyl or C₁-C₁₈alkyl/phenyl;is reacted with a compound of the formula Sn[R₂]₄  (IIb), in which R₂are, independently of one another, C₁-C₁₈alkyl, substituted C₁-C₁₈alkyl,C₂-C₁₈alkenyl, C₁-C₁₈haloalkyl, C₆-C₁₆haloaryl, C₃-C₁₆haloheteroaryl,C₁-C₄alkylphenyl, C₁-C₄alkoxyphenyl, halo-C₁-C₄alkylphenyl,halo-C₁-C₄alkoxyphenyl, C₁-C₁₂hydroxyalkyl, C₃-C₈cycloalkyl, C₆-C₁₆aryl,substituted C₆-C₁₆aryl, C₇-C₁₆aralkyl, C₃-C₆heterocycloalkyl,C₃-C₁₆heteroaryl, C₄-C₁₆heteroaralkyl, —Cl, —Br, —I, OH, —OC₁-C₁₈alkyl,—OC₆-C₁₆aryl, —OOC—C₁-C₁₈alkyl, —OOC-phenyl, SH, —N(Si(CH₃)₃)₂,SC₁-C₁₈alkyl, —SC₆-C₁₆aryl, —SC(O)—C₁-C₁₈alkyl, —SC(O)-phenyl,—SC(S)—C₁-C₁₈alkyl, —SC(S)-phenyl, H or an oxygen bridge to a further Snatom; or two radicals R₂ are together ═S or ═O, with the proviso that atleast one R₂ radical which can react with an SH group to form an S—Snbond is present.
 11. Process for preparing a tin(IV) compound bound toan inorganic support, characterized in that a compound of the formula

is reacted with a compound of the formula Sn(R₂)₄ to form animmobilizable Sn—S compound and this compound is immobilized on aninorganic support, where (R₁)′ is C₁-C₄alkyl or phenyl; (R₁)″ are,independently of one another, C₁-C₄alkoxy, phenoxy or halogen; and i is0, 1 or 2, with the proviso that w+i is less than or equal to 4; v is 1,2, 3 or 4; and w is 1, 2 or 3; L is an at least divalent C₁-C₁₈alkylene,C₂-C₁₈alkenylene, phenylene, C₁-C₁₈alkylene/phenylene radical or aC₂-C₁₈alkylene or C₁-C₁₈alkylene/phenylene radical interrupted by one ormore O, C(O), S, C(S), N(Y), C(O)—N(Y), N(Y)—C(O)—N(Y) and/orN(Y)—C(O)—O; Support is an inorganic support material; R₂ are,independently of one another, C₁-C₄alkoxy, phenoxy, C₁-C₄alkyl, phenylor halogen; and Y are, independently of one another, C₁-C₁₈alkyl, phenylor C₁-C₁₈alkyl/phenyl; n^(o) is 1, 2, 3 or 4; and M is H or an alkalimetal.
 12. Use of a tin(IV) compound comprising a radical of the formula

bound to an inorganic support, where L is an at least divalent radicaland at least one of the free valences of the Si in formula (I) is boundto the inorganic support, as catalyst in the transesterification ofcarboxylic esters.